Fix non working update dynamic settings

[dadoonet]

Described in https://github.com/elastic/elasticsearch/issues/10614, it's not possible with cloud discovery plugin to update dynamic settings anymore.

curl -XPUT localhost:9200/_cluster/settings -d '{
    "persistent" : {
        "discovery.zen.minimum_master_nodes" : 3
    },
    "transient" : {
        "discovery.zen.minimum_master_nodes" : 3
    }
}'

gives

{"acknowledged":true,"persistent":{},"transient":{}}

This patch makes that working again.

[dadoonet]

@imotov Could you review this PR please?

[imotov]

This change looks good to me, but I am wondering if we can somehow prevent this from happening in the future.

[imotov]

I have created PR that shows one possible way to prevent it. Not sure that it's the best way though.